Double Tap, I believe, allows you to carry three weapons at a time, rather than the default limitation of two. But when you start, you have one gun, the M1911 Pistol. Then the next gun you pick up is added, so that you can switch back to the M1911.
But from here, if you buy a gun, without double tap, the gun you were holding, you have lost. Say I spawn, kill a few dozen Zombies and buy the Olympia. I can switch back and forth between the Olympia and M1911. But say, I was holding the Olympia, went up to the M14, I lose the Olympia. But if I turn the power on, buy double tap, and do this process. I can switch between Olympia, M14 and M1911. Then say, I'm holding a M14, and decide to buy the MP40, I lose the M14. Hopefully, this was thorough enough to serve the purpose.
It means to shoot a zomie, then shoot it again to make sure it is dead.
(Watch zombieland the movie for more info.)
Double tap makes you fire your weapons faster
You need to buy double tap root beer, which on the zombies map Kino Der Toten is located in the alley.
Quick revive, juggernog or juggernaut, Speed Cola, and Double tap.
Double tap basically makes your gun shoot faster just like in Call Of Duty World at War.
Double Tap Root Beer increases the rate of fire of your weapons.
it depend sif your playing black ops zombies or world at war zombies black op zombies has stamin up double tap and PhD flopper regular world at war zombies has speed cola jugger nog and quick revive
Zombies: Root Beer- Double Tap Speed Cola - faster reloading Quick Revive - Revive Allies Faster Jugg-Nog - More Health
juggernog, speed cola, quick revive, mule kick, double tap rootbeer, stamin up, phd flopper, deadshot,
Makes your weapons shoot faster and increses recoil if anyone wants to talk about black ops 1 black ops 2 or world at war i know all the secrets hacks glitches aand everything of them contact me at andregoodarzi@hotmail.com
If by soda machines you mean the four different perks you can use in Black Ops Zombies, you can get Juggernaut (Increase in health), Quick Revive (self explanatory), Sleight of Hand (Quick reload), and Double Tap (Quicker shooting).
I think it is
Tap the triggers on consoles and go to the terminal and type 3arc unlock...or bear campaign
All you have to do is double tap the down button on the Plus pad.